The present invention relates generally to improvements in cast houses for blast furnaces, and specifically to an emissions recycle system for blast furnace cast houses.
A blast furnace in the steel industry is used to melt down iron ore, fluxes for forming slag, and other additions such as manganese ore or phosphoric rock, commonly called the "burden", to extract iron from the iron ore, the iron being in the form of pig iron. There is charged into the furnace in addition to the burden, fuel which is generally coke, and the air blast which is injected into the furnace to burn the fuel and to maintain a sufficiently high temperature to render both the iron metal and the resultant slag freely molten. The air blast at the requisite pressure is provided by a blower, which may be a steam-driven reciprocating engine, a steam-driven turboblower or a gas-driven reciprocating engine. Hot blast stoves are used for heating the air blast and each stove is composed of a mass of brickwork, arranged as checquer work, contained in a steel casing. The temperature of the brickwork is raised to the required level by the combustion of gaseous fuels therein. The gases are then shut off and the air blast from the blower is allowed to pass through the hot blast stoves on its way to the blast furnace. Two or more stoves are required in order that the process may be continuous.
The gases leaving the blast furnace at the top thereof, which gases are particulate laden, are passed through primary dust catchers and ultimately through gas washer towers where they are washed with water before use as one of the fuels fed to the hot blast stoves for heating the brickwork therein. The air which is heated in the hot blast stoves is introduced into the lower portion of the blast furnace for heating the burden which is introduced at the top of the blast furnace and works its way down into the lower portion of the blast furnace as it melts and as hot molten iron and hot molten slag are removed from the furnace. A tap hole is provided in the lower portion of the blast furnace that is opened periodically to allow molten metal to pour from the blast furnace. A cast house is provided adjacent to the blast furnace and contains runners into which the molten metal is poured. The runners in turn direct the molten metal to hot metal ladles or other containers which can then be removed from the cast house for use in steel making or in casting of the pig iron into small pieces called pigs. When the molten metal pours from the blast furnace, fumes are emitted in the cast house, and the total emissions during the process are substantial, and some emissions escape to the atmosphere through the roof monitor of the cast house.
Prior practice has dealt extensively with the collection and cleaning of the fumes from the top of the blast furnace, the following patents being exemplary of such prior art emissions collecting and cleaning systems: U.S. Pat. No. 2,345,067 granted Mar. 28, 1944 to B. Osann; U.S. Pat. No. 2,790,711 granted Apr. 30, 1957 to F. B. Sellers et al.; U.S. Pat. No. 3,041,059 granted June 26, 1962 to R. A. Powell; U.S. Pat. No. 3,460,934 granted Aug. 12, 1969 to J. J. Kelmar; and U.S. Pat. No. 3,928,023 granted Dec. 23, 1975 to H. B. Claflin. The problems of dealing with the fume emissions from the cast house monitor has not been successfully dealt with heretofore. Further, these prior systems are expensive because they require high volume blowers which consume large amounts of energy. They also require large spaces because of the use of large filter systems which also are expensive to install and operate.